Deadliest Heat Waves in US History, Including the 2021 Pacific Northwest Heat Dome

Two rankings and one rule: never compare a death count with an excess-mortality estimate without saying which is which. With station records and maps of how far temperatures ran above normal.

What was the deadliest heat wave in US history? By the widest measure, the summer of 1980: NOAA's billion-dollar disaster record, now kept by Climate Central, estimates about 10,000 deaths when indirect deaths from heat stress (excess mortality) are included, and its own death count of 1,260 is higher than for any other heat wave since its record began in 1980. The July 1936 heat wave killed about 5,000 people nationwide, according to the National Weather Service; no excess-mortality estimate exists for 1936, so the two cannot be ranked on one basis. The deadliest US city heat wave of modern times was Chicago's in July 1995: 739 more deaths than expected in one week. And the June 2021 Pacific Northwest heat dome, which drove Portland to 116°F and Seattle to 108°F, was the deadliest weather disaster in Washington State's history.

Why Heat Death Tolls Disagree

Heat kills quietly, often indoors and disproportionately among older people, so there is no single death count for a heat wave. Published figures come in three kinds, and they can differ by a factor of ten for the same event:

• Heat-related deaths are deaths that a medical examiner, coroner or death certificate attributes to heat. This is the narrowest count.
• Excess deaths are all deaths above the number expected for that place and time of year. They capture the heart attacks, kidney failures and strokes that heat brings on but that are not certified as heat deaths. This is the widest count, and the one epidemiologists trust most for big events.
• Surveillance totals are a county's or state's tally of heat deaths over a whole season or year, not one heat wave.

So the tables below keep the bases apart. The first ranks heat waves on a single basis. The second lists the deadliest heat waves on every basis that has been published, and says which is which.

The Deadliest Heat Waves Since 1980 (One Basis)

Ranking rule: every event in Climate Central's billion-dollar disaster dataset with "heat wave" in its name, 1980 to 2026 (20 events), ranked by the deaths the dataset records. Climate Central took over the dataset from NOAA's National Centers for Environmental Information (NCEI) in 2025. Each event is a heat wave combined with drought, so its dates span a season and its cost is mostly crop losses.

Source: Climate Central, U.S. Billion-Dollar Weather and Climate Disasters (events list read October 9, 2026). Common names in bold are ours. Next on the list: the 2012 drought and heat wave (123 deaths).

The dataset's own summaries show how much the basis matters. For 1980, it records 1,260 deaths but notes that "combined direct and indirect deaths (i.e., excess mortality) due to heat stress" were "estimated at 10,000". For 1988, it records 454 deaths and estimates excess mortality at 5,000. The Centers for Disease Control and Prevention (CDC), counting death certificates, attributed 1,700 deaths to heat in 1980 and 454 in 1988. The 2026 heat waves are in the dataset too, but with no death count yet: Climate Central says a fatality count "will be included in our end-of-year reporting".

The Deadliest US Heat Waves on Every Basis

These are the heat waves with the largest published death tolls, in date order. The figures use different bases, so they are not ranked against each other.

Sources: NWS Lincoln, IL; Climate Central; CDC MMWR; Whitman et al. 1997; NWS Natural Disaster Survey Report, July 1995 Heat Wave; Washington State Department of Health; University of Washington Climate Impacts Group; Oregon Health Authority; Hoshiko et al. 2010; Ostro et al. 2009; Maricopa County Department of Public Health.

The 2021 Pacific Northwest Heat Dome

For about a week at the end of June 2021, a ridge of high pressure parked over the Pacific Northwest and pushed temperatures to levels the region had never measured. The National Weather Service in Seattle described it as a long-duration, unprecedented heat wave from June 26 to July 2.

Temperatures. We checked every major weather station (NOAA GHCN-Daily "first-order" stations) in Washington, Oregon and Idaho with at least 30 years of data. Of the 43 we could evaluate, 24 set a new all-time high and 3 tied theirs between June 25 and July 2:

Source: NOAA NCEI GHCN-Daily station records, read October 9, 2026 (°F converted from the archived tenths of a degree Celsius). "Previous all-time high" is the station's highest reading before June 25, 2021, with the last year it was reached. All 27 record stations are on the map below.

Portland's previous record was beaten by 9°F and Salem's by 9°F; Quillayute, on the Pacific coast, beat its old record by 11°F. The University of Washington's Climate Impacts Group, with the Washington State Department of Health, counts 128 all-time high temperature records set across Washington, using every station in the state, not just the major ones.

Deaths. Washington's official estimate is 126 heat-related deaths; the Department of Health's final report counts 100 between June 26 and July 2 alone. The Oregon Health Authority counts 102 deaths caused by the heat dome. In Multnomah County, which includes Portland, 69 of the county's 72 heat deaths of 2021 came from the heat of the last week of June, against zero in a typical year; 68 of the 72 died in their own homes. Counting excess deaths instead, a 2023 report by the University of Washington's Climate Impacts Group and the Department of Health found 441 more deaths than expected between June 27 and July 3, after removing COVID-19 deaths. The same report calls the heat dome the deadliest weather-related disaster in Washington's history.

Chicago, July 1995: The Deadliest Modern Heat Wave in a US City

From July 12 to 16, 1995, daily highs in Chicago ranged from 93°F to 104°F, and on July 13 the heat index peaked at 119°F, a record for the city (CDC). The National Weather Service recorded 106°F at Midway Airport and 104°F at O'Hare, which tied O'Hare's all-time high from June 1988. The Cook County Medical Examiner certified 465 deaths as heat-related between July 11 and 27. From July 13 to 21, 1,177 people died in Chicago from all causes, 85% more than in the same days of 1994. A later study counted 739 excess deaths in the worst week alone, July 14 to 20. The NWS called it Chicago's worst weather-related disaster. In Milwaukee, the same heat wave killed 85.

The 1980 Heat Wave

The 1980 heat wave was long rather than sharp. In NOAA's gridded temperature analysis, daily highs across much of Kansas, Missouri, Oklahoma and north Texas averaged 5°F to more than 10°F above normal for the whole of July. Of 120 major weather stations with 30 years of data in the 13 affected states we checked, 19 set and 10 tied their all-time highs between June 20 and July 31, 1980, among them 117°F at Wichita Falls, Texas (June 28), 112°F at Dallas Love Field, 109°F at Little Rock, 108°F at Memphis and 105°F at Atlanta (records at the time; some have since been beaten). A 1982 study in JAMA found that deaths from all causes in July 1980 rose 57% in St. Louis and 64% in Kansas City compared with the two previous Julys, but only 10% in rural Missouri: heat waves kill most in cities.

Phoenix and the Longest Heat Waves

Arizona's heat waves are measured in weeks. At Phoenix Sky Harbor Airport, the high reached 110°F or more on 31 consecutive days, June 30 to July 30, 2023, by far the longest run in Phoenix's official record, which goes back to the 1890s; the next longest was 18 days in 1974. Maricopa County counted 645 heat-related deaths in 2023, the most it has ever recorded, then 608 in 2024 (a year with 70 days of 110°F or more at Sky Harbor) and 430 in 2025. These are calendar-year totals of deaths where heat was a cause or a contributing factor, not single heat waves, which is why they sit apart from the tables above.

Is 2026 One of the Worst?

By temperature, yes. In NOAA's Climate at a Glance national series, summer 2026 (June to August) was the hottest on record for the contiguous United States, at 74.37°F, ahead of 1936 and 2021 (both 73.98°F). By average daily high, 1936 still leads (87.89°F against 87.02°F in 2026), so the Dust Bowl summer of 1936 still has the highest average daily high on record.

In early July, a heat dome over the eastern half of the country set or tied all-time highs at 12 of the 226 major weather stations we checked from Illinois to New England and the Carolinas (June 28 to July 6), including 106°F at Langley Air Force Base, Virginia, a new record, and 106°F at Atlantic City International Airport, New Jersey, which tied the airport's record from 1969. These 2026 readings are preliminary until NOAA finishes its quality control. In Texas, the ERCOT grid set an unofficial all-time demand record of 91,089 megawatts on July 22, 2026. Phoenix reached 110°F on 39 days so far (preliminary).

By deaths, it is too early to say. No official national count exists yet, and Climate Central will add one at the end of the year. 2026 will join the rankings above when it does.

Map: How Hot It Got, and Where the Deaths Were Counted

The map shows how far daily highs ran above normal in three of the deadliest heat waves: the 2021 heat dome (June 25 to July 2), Chicago 1995 (July 11 to 16) and July 1980 (switch between them in the layer menu). Each is NOAA's gridded daily maximum temperature, averaged over those days, minus the 1991–2020 normal for the same days. The dots are the all-time station records from each event, and teal markers show where the death counts above were made. Off by default, you can also switch on DisasterAWARE heat alert records and the National Weather Service's heat warnings and advisories by forecast zone for California 2006, the 2021 heat dome, Phoenix 2023 and July 2026 (both ALERT tier: issued products, not measurements); the highest temperature reported at every station during the 1936, 1980, 1995, 2021 and 2026 heat waves; the heat index at airports at one afternoon hour on a peak day in 1995, 2021 and 2026; and outlines of the areas behind the local death counts (all but Milwaukee's).

Open map full screen ↗

What the map can show, by era. NOAA's gridded daily temperatures (NClimGrid) start in 1951, so every heat wave since then can be mapped this way; for 1936, only station records exist. NWS heat warnings survive in the Iowa Environmental Mesonet archive from 2005 (called extreme heat warnings since 2025), so there are none to map for 1936, 1980 or 1995. Station all-time records depend on each station's length of record, so they are clearest for long-running airport stations. Death counts are reported by city, county or state, so they appear as one marker per place, not as a map of where people died.

In the DisasterAWARE Archive Since 2014

DisasterAWARE's historical hazard archive holds 677 US heat records from August 2014 to September 2026 (pulled October 9, 2026): 244 warnings, 64 watches and 369 advisories. They are alerts, issued products, not temperature measurements or deaths. Since 2025 most of these records are issued per forecast area (111 in 2025 and 432 in 2026), so counts across years are not comparable. Here is what it recorded for the recent events above:

Counts: archive records of type EXTREMETEMPERATURE in the US named as heat alerts (or summer "extreme temperature" alerts), by start time, excluding exercise and test records. Source: DisasterAWARE Historical Hazards API, queried October 9, 2026. NWS warning times: Iowa Environmental Mesonet VTEC archive.

The population figures attached to alerts measure who lived inside the alert area, not who was affected, so we never rank heat waves by them.

For Insurers and Reinsurers: Heat Is a Mortality, Power and Productivity Peril

Heat rarely damages buildings, so it barely registers in property catastrophe models. Its losses fall on other lines.

• Mortality and health. Heat deaths land on life, health and long-term care books, concentrated among older people and people who live alone. In Multnomah County in 2021, 68 of the 72 heat deaths happened at home. Excess deaths can be several times the certified count (441 against 126 in Washington in 2021), so pricing from certified deaths alone understates the peril.
• Crops and drought. The losses in Climate Central's dataset are large because the heat waves came with drought: $57.8 billion for 1988, $44.1 billion for 2012, $43.0 billion for 1980, and $15.8 billion for 2023 (2026 dollars).
• Power demand and the grid. Heat drives peak electricity demand. ERCOT's all-time records are summer heat records: 85,508 MW on August 10, 2023, and an unofficial 91,089 MW on July 22, 2026. A heat wave that coincides with a generation shortfall turns into an outage, and an outage turns heat into business interruption, spoilage and more deaths.
• Labour productivity. A 2021 report from the Atlantic Council's Adrienne Arsht–Rockefeller Foundation Resilience Center estimated that heat already costs the US economy about $100 billion a year in lost labour productivity.
• Parametric covers. Because heat is measured, not inspected, it suits parametric triggers. In India in 2024, a heat-triggered income cover run by the Self-Employed Women's Association, with the insurer ICICI Lombard delivering the payouts, paid out about $350,859 to women working in the informal sector, more than 46,000 of them across 22 districts. Each region has its own trigger: in Ahmedabad, a daytime high above 43.6°C for two consecutive days. A trigger like that needs a defensible daily temperature record for the insured place, and a history of how often it has been crossed.

What event-level data exists. For a heat portfolio, the useful record is temperature, duration and footprint: NOAA's gridded daily temperatures go back to 1951 and station records further, and city, county and state health departments publish death counts on the bases described above. DisasterAWARE's archive adds the alerts themselves since 2014, each with its area and the population inside it: who was warned, where and when. Historical Event Intelligence licenses that archive across every hazard for back-testing, accumulation studies and event sets. The sample datasets show the record format with no signup.

Frequently Asked Questions

What was the deadliest heat wave in US history? By the widest measure, the 1980 heat wave and drought: NOAA's billion-dollar disaster record, now kept by Climate Central, estimates about 10,000 deaths including indirect deaths, and its own death count, 1,260, is the most of any heat wave since 1980. The July 1936 heat wave killed about 5,000 people, according to the National Weather Service, but on a basis that cannot be compared directly.

How many people died in the 2021 Pacific Northwest heat dome? Officially, 126 heat-related deaths in Washington (100 of them between June 26 and July 2, Washington State Department of Health) and 102 in Oregon (Oregon Health Authority). Counting excess deaths, Washington had 441 more deaths than expected between June 27 and July 3, 2021.

How many people died in the 1995 Chicago heat wave? The Cook County Medical Examiner certified 465 heat-related deaths between July 11 and 27, 1995. A 1997 study counted 739 excess deaths in the week of July 14 to 20.

What was the hottest heat wave in US history? By average daily high temperature across the contiguous US, the summer of 1936 (87.89°F, NOAA). By average temperature, summer 2026 is now the hottest on record, at 74.37°F, ahead of 1936 and 2021.

What is the longest heat wave in US history? The longest run of 110°F days in a major US city is Phoenix's 31 consecutive days, from June 30 to July 30, 2023, at Sky Harbor Airport; the next longest there was 18 days in 1974.

Related Reading

• Why Secondary Perils Are Changing Insurance Risk
• Extreme Heat Risk in Phoenix, AZ
• Extreme Heat Risk in Portland, OR
• Extreme Heat Risk in Seattle, WA
• Extreme Heat Risk in Chicago, IL

Sources: Climate Central billion-dollar disasters; NOAA NCEI GHCN-Daily, NClimGrid-daily, gridded climate normals and Climate at a Glance; National Weather Service (Lincoln, IL; Natural Disaster Survey Report, July 1995 Heat Wave); CDC MMWR; Whitman et al., American Journal of Public Health (1997); Jones et al., JAMA (1982); Washington State Department of Health; University of Washington Climate Impacts Group; Oregon Health Authority; Multnomah County; Maricopa County Department of Public Health; ERCOT; Atlantic Council Adrienne Arsht–Rockefeller Foundation Resilience Center; Insurance Journal; NPR (2025); Hoshiko et al., International Journal of Public Health (2010); Ostro et al., Environmental Research (2009); Iowa Environmental Mesonet (NWS VTEC archive); DisasterAWARE Historical Hazards API (queried 2026-10-09).